Auto-battle has 2 downsides for me as the audience:
- it takes away agency from the hero? Why exactly do we need Rimuru, when just about any reincanated slime could do the same?
- This turned out not being the case (and it makes no sense, honestly), but: Auto-battle the way it was described implies that it chooses all the best options in battle. Basically, Rimuru either dominates OR he's chanceless. That's boring, too.
Seeing Rimurs operators reaction, I wonder if that becomes important in the future.